Thermally responsive device



June 17, 1958 H. D. EPSTEIN 2,8

THERMALLY RESPONSIVE DEVICE Filed April 8, 195"? 2 Sheets-Sheet 1 172 new tor; Henry .Davz'd Zjus tez'n,

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Filed April 8; 1957 2 Sheets-Sheet 2 w M R NW R 1 Wm m m? nd 1m Henr United States Patent THERMALLY RESPDNSIVE DEVICE Henry David Epstein, Boston, Mass., assignor to Metals "85 Controls Corporation, Attleboro, Mass, at corporation of Massachusetts Application April 8,1957, Serial No. 651,469 s 'cnims. crew-'13s 1 This invention relates to an improved thermally responsive deviceyand more particularly, to such a device which includes a thermaly responsive, snap-acting means which is automatically snappable from one condition to another condition in response to temperature change.

Anobject of this invention is the provision of such an improved device which, to an observer, is capable of reliably indicating the conditioner position in which the snap-acting means is disposed even though the latter be hidden from the observers view.

A further object of this invention is the provision of such an-improved device which is capable of providing said indicating function directly in response to the action of said snap-actingmeans.

A further object of this invention is to provide such an improved device which is capable of effecting said indicating functionwithout engagement with and/ or loading of the snap-acting means by the means which provides the indicating function while the snap-acting means is in one of said conditions.

A further object of this invention is the provision of a mechanically resettable, thermally responsive, snapacting device wherein the means for mechanically resetting the snap-acting means provides said indicating function.

A further object of this invention is the provision of such an improved device which is capable of so eitecting said indicating function and which is trip-free.

A further object of this invention is the provision of such a device which is simple in construction, economical to manufacture and dependable in operation.

Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises'the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of the various possible embodiments of the invention is illus trated:

Fig. 1 is'a top plan view of a circuit breaker constructed according to this invention;

Fig. 2 is a view similar to Fig. 1, but showing the circuit breaker with the cover and a gasket removed therefrom;

Fig. 3 is a sectional view taken along line 33 in Fig. 1, but with portions of certain of the parts along the section line being shown in full;

Fig. 4 is a view similar to Fig. 3 but showing the pushbutton and resetting member in fully depressed position; and

Fig. 5 is a sectional view taken along line 55 in Fig. 4, but with certain portions along the section line being shown in full.

Referring to the drawing, an exemplary construction is shown which incorporates the present invention. This construction takes the form of a circuit breaker generally 2,839,637 Patented June 17, 1958 indicated by the numeral 10, and includes a base 12 formed of insulating material such as one of the customary molded plastics. Base 12 is provided with a bore 14 within which a bushing 16 is fixedly secured. A supporting post 18 is disposed in adjustably threaded engagementwith bushing 16 and, along with base 12, provides supporting means for a composite, thermally responsive, snap-acting element 20.

Snap-acting element 20 is formed of several layers of material having mutually difierent coefficients of expansionas disclosed, for example, in U. S. Patent No. 1,448,240 to J. A. Spencer, and is provided with a substantially centrally disposed aperture 22. Snap-acting element 20 is mounted on post 18 between the flanges provided by members 24 and 26, respectively; a reduceddiameter, cylindrical portion 27 of flange-providing member 24 lying within aperture 22. The flanges provided by members '24 and 26 retain snap-acting element 20 therebetween in non-binding relation thereto. In this regard, snap-acting element 2% is substantially freely rotatable relative to supporting post 18, but is prevented from substantial movement longitudinally of the supporting post. Snap-acting element 20 is automaticaly snappable in response to temperature change (for example, due to heating thereof upon the flow of a current overload therethrough) from the downwardly bowed condition shown in broken lines in Fig. 3 and in full lines in Figs. 4 and 5 to the upwardly bowed condition shown in all lines in Fig. 3. However, snap-acting element 29 is preferably incapable, under normal temperature conditions, of automatically snapping from the upwardly bowed condition back to said downwardly bowed condition in response to temperature change in the opposite direction. Normal temperature conditions are meant to be such conditions as the device may be expected normally to encounter. Snap-acting element 2t. carries a pair of spaced contacts 28 and 30, respectively, which may be secured thereto by any suitable means such as by welding. Conventional welding caps 32 and 34 may be utilized to facilitate the welding operation and to improve the resulting weld.

When the snap-acting element is in the downwardly bowed condition (see Fig. 5), contacts 28 and 30 are disposed in electrically conductive engagment with contacts 36 and 38, respectively, whereby contacts 36 and 38 are electrically connected by the snap-acting element. With snap-acting element 20 in said upwardly bowed condition as shown in full lines in Fig. 3, contacts 23 and 30 are separated from contacts 36 and 38, respectively, and the latter two contacts are electrically disconnected from each other. Contacts 36 and 38 are carried by terminals 40 and 42, respectively, these terminals being fixedly mounted on the base in any suitable manner.

A sleeve 44 having a flange 46 is disposed about supporting post 18 and, by heading over the supporting post at 48, this sleeve, along with flange-providing members 24 and 26, and snapacting member 20, is retained on the supporting post. Circuit breaker 10 includes means -for resetting the snap-acting element by mechanically snapping the latter from its upwardly bowed condition to its downwardly bowed condition. in this regard, a collar 50 is slidably mounted on sleeve 4- for longitudinal movement with respect to the sleeve and post 13 within limits determined by engagement of the collar with flange 46 at one end and the flange provided by member 26 at the other end. Collar 5 is force-fit within a socket 52 provided by a push-button 54 whereby this collar and the push-button are fixed with respect to each other. The resetting means further includes a resetting member 56 which is provided with a pair of spaced projections 58 and60, each of which is engageable with the snap-acting assaesv If a.) element 20. It will be apparent that, by depression of push-button 54 from the position shown in Fig. 3 to the full-line position shown in Figs. 4 and 5, the projections carried by the resetting member will be moved against the snap-acting element thereby to snap the latter from the upwardly bowed condition shown in full lines in Fig. 3 to the downwardly bowed condition shown in Figs. 4 and 5.

Circuit breaker is so adjusted that, when snap-acting element is in said downwardly bowed condition, full depression of the push-button will be incapable of moving resetting member 56 including projections 58 and 60 into engagement with the snap-acting element. In this regard, flange-providing member 26 acts as a stop means when engaged by the adjacent portions of collar 50 and resetting member 56 to prevent movement of the latter including the projections carried thereby against the snapacting element when this element is in said downwardly bowed condition while permitting movement of the resetting member against the snap-acting element past the point at which the latter snaps from said upwardly bowed condition to said downwardly bowed condition. In this manner, trip-free operation of the circuit breaker is effected.

By trip-free operation, it is meant that snap-acting element 20, when heated to or above the temperature at which it would normally snap from said downwardly bowed condition to the upwardly bowed condition, cannot be maintained in its downwardly bowed, contactsclosed condition by forcibly holding the push-button in its fully depressed position. It follows that when the device is trip-free and the snap-acting element is above the maximum resetting temperature, full depression of the push-button is not effective to snap the snap-acting element from said upwardly bowed condition to said downwardly bowed condition.

Resetting member 56 carries an extension 62 having a projection 64 thereon which interfits with a complementary groove 66 provided by the internal wall of base 12. In this manner, substantial rotation within base or casing 12 of resetting member 56 and the structure fixed with respect thereto is prevented. Substantial rotation of snap-acting element 20 within the casing may likewise be prevented by providing the snap-acting element with a projection (not shown) interfitting with groove 66 in like manner.

Push-button 54 has a flange 68 forming a shoulder 70 for a purpose later to be described. Push-button 54 extends from the interior of base 12 through cover means provided by the device to the exterior thereof. The cover means ofcircuit breaker 10 includes a cover member 72 and a gasket 74 formed of insulating material such as rubber, both of which may be secured in place by means of bolts or screws disposed in apertures 76 and 78 provided by base 12. Cover member 72 is provided with an aperture 80 within which a spring-retaining member 82 is disposed. Member 82 is provided with a flange 84 which is biased against gasket 74 and cover member 72 by means of a compression spring 86. Spring 86 bears against member 82 at one end and against shoulder 70 provided by flange 68 at the other end whereby the resetting member and the push-button are yieldingly biased by the spring in a direction toward the snap-acting element. It will be apparent that members 72 and 82 could conveniently be formed as a one-piece construction, whereby the construction of gasket 74 would, of course, be altered to accommodate such a construction.

When snap-acting element 2%) is in the downwardly bowed condition shown in Figs. 4 and 5, push-button 54 and resetting member 56 will be disposed in fully depressed position under the bias of spring 86. Upon snapping of the snap-acting element to the upwardly bowed condition due, for example, to the occurrence of a current overload flowing through the snap-acting element,

the respective portions of the snap-acting element adja- 4, cent each of projections 55 and 60 will be snapped from the position shown in Fig. 4 to the tripped position shown in full lines in 'Fig. 3. The effect is that these respective portions of the snap-acting element are moved into e11- gagement and against projections 58 and 60 whereby the resetting member and push-button 54 are moved against the yielding bias of spring 86 to the position as shown in Fig. 3. It will be noted that in the exemplary construction shown in the drawing, the extent of this up ward movement of the resetting member and the pushbutton is limited by the engagement of collar 50 with flange 46 as provided by sleeve 44. It will be apparent, then, that so long as snap-acting element 20 is in its downwardly bowed condition, push-button 54 will be biased by spring 86 to its fully depressed position, and so long as snap-acting element 20 is in its upwardly bowed condition the push-button will be biased to its fully retracted position by the snap-acting element. When the pushbutton returns to its fully retracted position upon release from full, forcible, external depression thereof, it is clear that the snap-acting element is at a temperature above the maximum resetting temperature and that this ele ment is in the upwardly bowed condition shown in full lines in Fig. 3. Also, except when the push-button isbeing forcibly retained in its fully depressed position by external means, the push-button will be disposed in depressed position only when the snap-acting element is in the downwardly bowed condition shown in Figs. 4 and 5. The result is that, unless an external force is applied to the push-button, the snap-acting element will be disposed in said downwardly bowed condition when the push-button is in its fully advanced or depressed position, and the snap-acting element will be disposed in said upwardly bowed condition when the push-button is in its fully retracted position. In this manner collar 50, resetting member 56 and push-button 54 act as indicating means to denote the position or condition in which snapacting element 20 is disposed.

It will be noted that means, such as a stripe in the form of an inlaid band 88 of a color or appearance contrasting with that of the remainder of the push-button,

-may be provided to indicate clearly the relative position of the push-button and, in turn, the corresponding position or condition of resetting member 56 and snapacting element'20. In this regard it is noted that stripe 88 is hidden behind member 82 when the snap-acting element is in the downwardly bowed condition (see Figs. 4 and 5) and is at least partially exposed to view when the snap-acting element is in said upwardly bowed condition (see Fig. 3).

One of the advantageous features of this construction is that the movement of push-button 54 to the fully retracted position shown in Fig. 3 is directly responsive to movement of the respectively adjacent portions of the snap-acting element against projections 58 and 60 of resetting member 56.

One difliculty with a construction whereby at least a portion of the means which provides the indicating function is directly responsive to the action of the snap-acting element is that engagement of any means with the snap-acting element and/or loading of the element will 'afiect and alter the thermal and mechanical characteristics of this element. This, of course, leads to problems in calibration and overall operation of the device. This difliculty is obviated with the present invention simply by so adjusting the parts as to render the circuit breaker trip-free as explained above. The device being trip-free, flange-providing member 26 acts as a stop means in preventing movement of resetting member 56 into engagement with the relatively adjacent portions of the snap-acting element while these portions are in the downwardly bowed or reset position as shown in full lines in Fig. 3. Accordingly, so long as snap-acting element 20 remains in the downwardly bowed condition,

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this element cannot beengagedor loaded by the resetting means, and the thermal and mechanical characteristics of the snap-acting element are unaffected thereby. It will be clear therefore that by this invention the indicating function and the trip-free function accommodate each other to provide the added feature whereby loading of and/or engagement with the snap-acting element by the indication-effecting means is obviated when the element is in the contacts-closed position.

in view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In combination: a base; a composite, thermally responsive, snap-acting element carried by said base; said snap-acting element being automatically snappable from a first condition to a tripped condition in response to temperature change; resetting means yieldingly biased in a first direction toward said snap-acting element; means mounting said resetting means for movement in said first direction against said snap-acting element to snap the latter from said tripped condition to said first condition; said snap-acting element, upon snapping thereof from said first condition to said tripped condition, being movable against said resetting means to move the latter against said yielding bias and in a direction opposite to said first direction.

2. In combination: a composite, snap-acting element automatically snappable from a first condition to a tripped condition in response to temperature change in one direction; a member; means mounting said member for movement from a first position to a second position; means yieldingly biasing said member from said first position toward said second position; said snap-acting element, in said tripped condition, engaging and retaining said member in said first position against the yielding bias of said biasing means and, in said first condition, permitting movement of said member under said yielding bias from said first position toward said second position; and stop means operatively associated with said member for preventing movement of said member under said yielding bias past said second position and into engagement with said snap-acting element when the latter is in said first condition.

3. A thermally responsive, mechanically resettable, trip-free device comprising: a composite, thermally responsive, snap-acting element; said snap-acting element being responsive to temperature change in one direction automatically to snap from a first condition to a tripped condition; resetting means mounted for movement between two positions in opposite directions toward and away from said snap-acting element; means yieldingly biasing said resetting means in the direction toward said snap-acting element; said snap-acting element, in said tripped condition, engaging and retaining said resetting means in said first position against the yielding bias of said biasing means and, in said first condition, permitting movement of said resetting means under said yielding bias from said first position toward said second position; and stop means operatively associated with said resetting means to prevent movement of the latter under said yieiding bias past said second position thereby to permit snapping of said snap-acting element from said first condition toward said tripped condition while said resetting means is forcibly retained in said second position.

4. In combination: a base; a composite, thermally re sponsive, snap-acting element carried by said base; said snap-acting element being automatically snappable from a CD I first condition to a tripped condition in response to temperature change correspondingly to snap a first portion of said element from a first position to a tripped position; resetting means movable in a first direction against said portion of the snap-acting element for snapping said portion from said tripped position to said first position; means yieldingly biasing said resetting means in said first direction toward said portion of the snap-acting element; and stop means preventing movement of said resetting means into engagement with said portion of the snapa' ing element when said portion is in said first position; said portion of the snap-acting element, upon tripping of said snap-acting element, being movable against said resetting means thereby to move the latter against the force exerted by said biasing means and in a direction opposite to said first direction.

5. In combination: a casing; a composite, thermally responsive, snap-acting element supported by said casing; said snap-acting element including a portion automatically snappable from a first position to a tripped position in response to temperature change; a first member extending outside said casing; a resetting member operatively connected to said first member and movable in a first direction against said portion of the snap-acting element for snapping said portion from said tripped position to said first position in response to movement of said first member in a corresponding direction; means resiliently biasing said first member in said corresponding direction and resiliently biasing said resetting member in said first direction; and stop means preventing movement of said resetting means into engagement with said portion of the snap-acting element when said portion is in said first position; said portion of the snap-acting element, upon tripping th reof, being movable against said resetting means thereby to move the latter in a direction opposite to said first direction and to move said first member in :1 direction opposite to said corresponding direction.

6. In combination: a hollow casing; a supporting post carried by said casing; a composite, thermally responsive, snap-acting element disposed within said casing and mounted on said supporting post; said snap-acting element being automatically snappable from a first condition to a tripped condition in response to temperature change; a resetting member disposed within said casing and movable against said snap-acting element to snap the latter from said tripped condition to said first condition; a push-button fixed with respect to said resetting member and having a shoulder thereon; cover means secured to said casing and provided with an aperture therein; said pusi1-button extending from the interior of said hollow casing through said aperture to the exterior of said cover means; a compression spring disposed between said shoulder and said cover means for yieldingly biasing said resetting member toward said snap-acting member; and stop means preventing movement of said resetting means against said snap-acting member under the bias of said spring when the snap-acting element is in said first condition.

7. in combination: snap-acting means including a portion snappable from one position to another position; including a member movable against said portion in a first direction from a first position of said member to a said other position to said one position; and means resiliently biasing said member in said first direction for yieldingly retaining said member at said second position until moved to said first position by snapping of said portion from said one position to said other position.

8. in combination; snap-acting means including a portion snappable between a first position and a second position; means including a member movable against said portion in a first direction to snap said portion from said second position thereof to reset said portion from first position to said second position; means resiliently biasing said member toward said portion and in said first direction; and stop means permitting movement of said member in said first direction to the position at which said portion snaps to said second position and preventing movement of said member in said first direction into engagement with said portion While the latter is in said second position.

References Cited in the file of this patent UNITED STATES PATENTS Bolesky May 7, 19,40 ONeill Dec. 7, 1954 Mang Mar. 15, 1955 Cataldo et a1 July 31,, 1956 

